/*
 * Reference.java January 2010
 *
 * Copyright (C) 2010, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.convert;

import wx.xml.simpleframework.xml.strategy.Value;

/**
 * The <code>Reference</code> object represents a value that holds
 * an object instance. If an object instance is to be provided from
 * a <code>Strategy</code> implementation it must be wrapped in a
 * value object. The value object can then provide the details of
 * the instance and the actual object instance to the serializer.
 *
 * @author Niall Gallagher
 */
class Reference implements Value {

    /**
     * This represents the original value returned from a strategy.
     */
    private Value value;

    /**
     * This represents the object instance that this represents.
     */
    private Object data;

    /**
     * This is the actual type of the reference that is represented.
     */
    private Class actual;

    /**
     * Constructor for a <code>Reference</code> object. To create
     * this a value and an object instance is required. The value
     * provided may be null, but the instance should be a valid
     * object instance to be used by the serializer.
     *
     * @param value  this is the original value from a strategy
     * @param data   this is the object instance that is wrapped
     * @param actual this is the overriding type of the reference
     */
    public Reference(Value value, Object data, Class actual) {
        this.actual = actual;
        this.value = value;
        this.data = data;
    }

    /**
     * This will return the length of an array reference. Because
     * the value will represent the value itself the length is
     * never used, as no instance needs to be created.
     *
     * @return this will always return zero for a reference
     */
    public int getLength() {
        return 0;
    }

    /**
     * This is the type of the object instance this represents. The
     * type returned by this is used to instantiate an object which
     * will be set on this value and the internal graph maintained.
     *
     * @return the type of the object that must be instantiated
     */
    public Class getType() {
        if (data != null) {
            return data.getClass();
        }
        return actual;
    }

    /**
     * This returns the actual object instance that is held by this
     * reference object.
     */
    public Object getValue() {
        return data;
    }

    /**
     * This is used to set the value of the object. If the internal
     * <code>Value</code> is not null then the internal value will
     * have the instance set also.
     *
     * @param data this is the object instance that is to be set
     */
    public void setValue(Object data) {
        if (value != null) {
            value.setValue(data);
        }
        this.data = data;
    }

    /**
     * This will always return true as this <code>Value</code> object
     * will always contain an object instance. Returning true from
     * this method tells the serializer that there is no need to
     * actually perform any further deserialization.
     *
     * @return this always returns true as this will be a reference
     */
    public boolean isReference() {
        return true;
    }
}